Does Smarty charge extra for texts using RCS Chat?

Hi. I'm new to Smarty, and have just moved over from EE.

With EE, if I sent a text message that wasn't an SMS (eg, a text that used a smiley, or was extra long, I'd be charged extra for conversion to MMS)

I'd like to switch to RCS Chats for text messaging, but have no idea if this is chargeable outside of my Smarty unlimited plan.

I also believe the recipient has to also use RCS Chat, and I'm having problems explaining the settings to an elderly relative..

Many thanks in advance.